Bulletin of the American Physical Society
2015 Fall Meeting of the APS Division of Nuclear Physics
Volume 60, Number 13
Wednesday–Saturday, October 28–31, 2015; Santa Fe, New Mexico
Session FE: Nuclear Structure - Light Nuclei |
Hide Abstracts |
Chair: Calem Hoffman, Argonne National Laboratory Room: Sweeney Ballroom D |
Thursday, October 29, 2015 4:00PM - 4:12PM |
FE.00001: New Measurement of the $^{5}$H Ground State Daniel G. McNeel, A.H. Wuosmaa, S. Bedoor, A.S. Newton, K.W. Brown, R.J. Charity, L.G. Sobotka, W.W. Buhro, Z. Chajecki, W.G. Lynch, J. Manfredi, R.H. Showalter, M.B. Tsang, J.R. Winklebauer, S.T. Marley, D.V. Shetty We have studied the ground state of $^{5}$H using the $^{6}$He($d$,$^{3}$He)$^{5}$H reaction in inverse kinematics. Existing data for $^{5}$H are in conflict with each other and with many theoretical predictions. This measurement provides a clear evidence for the $^{5}$H ground state, and the previously unreported $^{6}$He($d$,$t)^{5}$He$_{g.s.}$ reaction is also observed. A $^{6}$He beam at 55 MeV/A produced at the National Superconducting Cyclotron Laboratory at Michigan State University bombarded a 1.9 mg/cm$^{2}$ (CD$_{2})_{n}$ target. The reaction products were detected with HiRA (the High Resolution Array). The $^{3}$He and $^{3}$H particles from the $^{6}$He($d$,$^{3}$He/$^{3}$H)$^{5}$H/$^{5}$He reactions were detected in coincidence with the decay products of the unstable $^{5}$H and $^{5}$He nuclei, providing signatures for the transitions of interest. The properties of the $^{5}$He ground state provide information about the calibration and response of the apparatus. Details of the measurement, and a comparison of the data with earlier results and theoretical calculations, will be presented. [Preview Abstract] |
Thursday, October 29, 2015 4:12PM - 4:24PM |
FE.00002: Few-Nucleon Charge Radii and a Precision Isotope Shift Measurement in Helium Nima Hassan Rezaeian, David Shiner Recent improvements in atomic theory and experiment provide a valuable method to precisely determine few nucleon charge radii, complementing the more direct scattering approaches, and providing sensitive tests of few-body nuclear theory. Some puzzles with respect to this method exist, particularly in the muonic and electronic measurements of the proton radius,~known as the proton puzzle. Perhaps this puzzle will also exist in nuclear size measurements in helium. Muonic helium measurements are ongoing while our new~electronic results will be discussed here.~~We measured precisely the isotope shift of the 2$^{\mathrm{3}}$S - 2$^{\mathrm{3}}$P transitions in~$^{\mathrm{3}}$He and~$^{\mathrm{4}}$He.~~The result is almost an order of magnitude more accurate than previous measured values.~~To achieve this accuracy, we implemented various experimental techniques. We used a tunable laser frequency discriminator and electro-optic modulation technique to precisely control the frequency and intensity.~ We select and stabilize the intensity of the required sideband and eliminate unused sidebands.~ The technique uses a MEMS fiber switch (t$_{\mathrm{s}}$~$=$ 10 ms) and several temperature stabilized narrow band (3 GHz) fiber gratings.~ A beam with both species of helium is achieved using a custom fiber laser for simultaneous optical pumping.~ A servo-controlled retro-reflected laser beam eliminates Doppler effects.~~Careful detection design and software are essential for unbiased data collection. Our new results will be compared to previous measurements. [Preview Abstract] |
Thursday, October 29, 2015 4:24PM - 4:36PM |
FE.00003: Continuum response functions from the R-matrix and Lorentz Integral Transform method W. Erich Ormand, Michael Kruse, Calvin Johnson Strength functions are an excellent tool to determine the collective excitation mechanism of a nucleus. In previous work we analyzed the giant dipole resonance of Boron-10 as calculated through Lanzcos strength function techniques and the No Core Shell Model (NCSM); a many-body bound state technique which uses as input realistic two- and possibly higher body forces. Since we only calculate bound states we need to introduce a posteriori a finite width for the transition matrix elements in the strength function. We present here two ways of including continuum physics into the discrete strength function: the R-matrix formulation of neutron escape widths and the Lorentz Integral Transform (LIT) method. To calculate the GDR of Boron-10 we implemented an R-matrix formulation of neutron escape widths; our calculations agree with experimental cross section data, and are different from those obtained with the LIT. We discuss both the R-matrix and LIT method, paying special attention to the physics contained in each method, and for the LIT provide an uncertainty estimate based on a chi-square analysis of the reconstructed response function. [Preview Abstract] |
Thursday, October 29, 2015 4:36PM - 4:48PM |
FE.00004: Structure of 10N via 9C+p Resonance Scattering Joshua Hooker, Grigory Rogachev, Yevgen Koshchiy, Ethan Uberseder, Heshani Jayatissa, Curtis Hunt, Brian Roeder The study of $^{10}N$ through the reaction $^{9}C(p,p)^{9}C$ using a new time projection chamber (TexAT-P1) at the Cyclotron Institute at Texas A\&M University. Only one experiment before this study on $^{10}N$ has claimed to have observed the ground state. We build on this result by providing a spin-parity assignment of the ground state and low-lying excited states in $^{10}N$. The mirror nucleus, $^{10}Li$, is not well known and also has uncertainty its spin-parity assignments and excitation energies in low-lying states. This nucleus is important to study as it can help explain the two neutron halo nucleus $^{11}Li$ as its nuclear matter radius is as large as that of $^{208}Pb$. [Preview Abstract] |
Thursday, October 29, 2015 4:48PM - 5:00PM |
FE.00005: ABSTRACT WITHDRAWN Keri Kuhn, Fred Sarazin One-neutron transfer reactions are being used to study single-particle neutron states in nuclei. For one-neutron halo nuclei, such as $^{11}$Be, the (p,d) reaction enables the removal of the halo neutron or of one of the core neutrons. This way, it is possible to simultaneously study the halo wavefunction of the $^{11}$Be ground-state but also a possible excited halo state in $^{10}$Be. The $^{11}$Be(p, d)$^{10}$Be transfer reaction at 10 MeV/nucleon is being investigated at the TRIUMF-ISAC II facility with the Printed Circuit Board Based Charged Particle ((PCB)$^2$) array inside the TRIUMF ISAC Gamma-Ray Escape-Suppressed Spectrometer (TIGRESS). The ground state and first excited state of $^{10}$Be can be directly identified using deuteron identification and kinematics from the charged particle array, while the four excited states in$^{10}$Be around 6 MeV, including the suspected halo state ( 2$^-$ state), are identified using coincident gamma rays from TIGRESS with the identified deuterons. Angular distributions for the $^{10}$Be populated states will be shown along with their FRESCO fits. [Preview Abstract] |
Thursday, October 29, 2015 5:00PM - 5:12PM |
FE.00006: New precision lifetime measurement of the $2_1^+$ state of $^{12}$Be C. Morse, C.J. Lister, P. Chowdhury, E. Merchan, V.S. Prasher, E.A. McCutchan, T.D. Johnson, A.A. Sonzogni, H. Iwasaki, V.M. Bader, D. Bazin, S. Beceiro-Novo, A. Gade, C. Loelius, E. Lunderberg, F. Recchia, D. Weisshaar, K. Whitmore The $^{12}$Be nucleus exhibits a tension between two different nuclear structure effects: strong $\alpha$-clustering characteristics similar to $^{8,10}$Be, and a tendency towards spherical, single-particle behavior due to the canonically magic neutron number $N=8$. The observed drop of 1.2~MeV in its $2_1^+$ energy compared to $^{10}$Be suggests that the $N=8$ magic number breaks down in this nucleus, instead giving way to clustering. However, the previously determined $B(E2;2_1^+\rightarrow 0_1^+)$ strength lacks sufficient precision to ascertain whether $^{12}$Be is more elongated than $^{10}$Be, which is a critical test of the exact role of the valence neutrons. To resolve this issue, a new experiment has been performed using GRETINA with the Doppler shift attenuation method to determine the lifetime of the $2^+_1$ state with better than 10\% precision. Preliminary results from the analysis will be presented and the implications for the structure of $^{12}$Be will be discussed. [Preview Abstract] |
Thursday, October 29, 2015 5:12PM - 5:24PM |
FE.00007: Study of $^{12}$Be using the $^{11}$Be($^{9}$Be,$^{8}$Be) transfer reaction at TRIUMF ISAC-II Ryan Braid, Fred Sarazin Recent results at TRIUMF and NSCL have called into question the structure of $^{12}$Be, therefore another look at this nucleus is desirable. The structure is important information for theoretical models, since it constrains the mechanism that produces parity inversion in $^{11}$Be. The $^{12}$Be structure was probed in July 2014 using the (PCB)$^2$ array (Printed Circuit Board Based Charged Particle) inside TIGRESS (TRIUMF - ISAC Gamma Ray Escape Suppressed Spectrometer) at TRIUMF using the $^{11}$Be($^9$Be,$^8$Be)$^{12}$Be reaction at 55 MeV in inverse kinematics. A second set of data at 30 MeV was collected. This reaction has numerous advantages over the traditional (d,p) method, foremost of which is the $^8$Be $\rightarrow$ 2 $\alpha$ breakup since it allows for very clean identification and tagging. Additionally, TIGRESS will allow precise $\gamma$-tagging for the excited states. The initial data and analysis will be presented in this talk. This work is partially supported by the US Department of Energy through Grant/Contract No. DE-FG03- 93ER40789 (Colorado School of Mines). [Preview Abstract] |
Thursday, October 29, 2015 5:24PM - 5:36PM |
FE.00008: 3-Body Decay of Cluster States in $^{14}$C Adam Fritsch, Yassid Ayyad Limonge, Daniel Bazin, Saul Beceiro-Novo, Joshua Bradt, Wolfgang Mittig, Tan Ahn, Alan Howard, J.J. Kolata, Fred Becchetti, Michael Wolff The clustering of $\alpha$ particles in nuclei results in the self-organization of various geometrical arrangements, informing our understanding of nuclear structure and nuclear astrophysics. In a previous experiment, the Prototype Active-Target Time-Projection Chamber was used to investigate $^{14}$C cluster structures by way of a 38~MeV secondary $^{10}$Be beam incident on a 90:10 He:CO$_2$ active target gas at the University of Notre Dame. The $^{10}$Be beam was produced by TwinSol and delivered to the Prototype AT-TPC. In addition to measuring elastic and inelastic $^{10}\mathrm{Be}~+~\alpha$ resonances, evidence of 3-body decays of $^{14}$C were observed in the data. Thus, additional data were later taken with an updated trigger scheme more sensitive to 3-body $^{14}$C decay events. Preliminary analysis of this data will be discussed and presented. [Preview Abstract] |
Thursday, October 29, 2015 5:36PM - 5:48PM |
FE.00009: Search for $\alpha$-cluster structure in $^{14}$O T. Ahn, J. Allen, D.W. Bardayan, B. Becker, W. Boeschenstein, K. Cushman, M. Hall, O. Hall, J. Hu, J. Koci, L. Jensen, J.J. Kolata, P. O'Malley, Y. Ayyad, D. Bazin, S. Beceiro Novo, J. Bradt, M. Cortesi, L. Carpenter, W. Mittig, F.D. Becchetti $\alpha$-cluster structure in exotic nuclei is an emergent many-body phenomenon that is an important ingredient in nuclear structure. Evidence for $\alpha$-cluster structure has been found for states in $^{14}$C, an example of $\alpha$ cluster structure existing with additional neutrons. On the proton-rich side, the question remains if clusters states exist in the isospin mirror $^{14}$O. A secondary beam of $^{10}$C was produced using TwinSol at the University of Notre Dame to probe states in $^{14}$O using $\alpha$-resonant scattering. The Prototype Active-Target Time-Projection Chamber was used to measure differential cross sections. These cross sections should give a strong constraint to cluster models and help elucidate whether isospin is preserved in cluster states. Preliminary results for the recently performed experiment will be presented. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700